CuInSe2 (CIS), which is a typical chalcopyrite, has a very high solar cell efficiency up to 17% and has generally been prepared through high vacuum process fabricating thin films, including selenization processes, which comprise vacuum deposition, the decomposition and deposition of organometallic compounds, electrochemical deposition or sputtering, or solid phase reactions, which requires a high synthetic temperature higher than 600° C. (U.S. Pat. Nos. 5,356,839 and 5,045,409; Thin Solid Films 1994, 245,174, Chem. Mater. 2003, 15, 3142). However, these methods have problems which includes expensive equipment and high energy costs.
Carmalt et al. could obtain CuInSe2 at a relatively low temperature after carrying out a reflux reaction for 72 hours. However, in this method the heat treatment at a temperature higher than 500° C. must necessarily be carried out in order to obtain crystalline CuInSe2 (J. Mater. Chem. 1998, 8 2209).
Li, Yang, Chun et al. reported that CIS particles were synthesized at low temperature through a solvothermal method from copper dichloride (CuCl2), indium trichloride (InCl3) and selenium (Se) powders as raw materials using an amine compound as a solvent or a chelating agent (Adv. Mater. 1999, 11, 1456, J. Phy. Chem. 2006, 110, 17370; Korean Patent Laid-Open Publication No. 10-2005-0037495). However, this method needs long reaction time (more than 12 hours) and the CuSe and Se powders remain in trace amounts.
A reflux reaction method that uses microwaves as a heat source in the solvothermal synthesis of CIS was reported (Inorg. Chem. 2003, 42, 7148). In this method, even though the reaction is completed within a short synthesis time (1 hour), CuSe-associated impurities remain and the crystallinity of the product is relatively low, and there is a limitation in carrying out a continuous preparation process commercially producing CIS. In addition, even though polyol, used as a reaction solvent in this method, it is generally used as a reducing agent and it can cause oxidation of CIS, because it contains oxygen in the molecule.
Thus, there is a general need for a method of preparing chalcopyrite-type compound that avoids or solves one or more of the above-mentioned problem of prior art methods. There is particular need for a method of preparing chalcopyrite-type compounds having high crystallinity and/or little or no impurities. For purposes of process efficiencies, there is also need for a method of preparing chalcopyrite-type compound having a short reaction time and little to no unreacted materials